MDEV-9141 : [PATCH] Add CA validation to wsrep_sst_xtrabackup-v2.sh

- Add CA validation to wsrep_sst_xtrabackup-v2.sh.
- Also added a few {} around tpem for consistency.
- Abort if encryption is requested but socat is not ssl-enabled.

Patch contributed by : Klaas Demter

scripts/wsrep_sst_xtrabackup-v2.sh

@@ -191,9 +191,9 @@ get_transfer()
             exit 2
         fi
 
-        if [[ $encrypt -eq 2 || $encrypt -eq 3 ]] && ! socat -V | grep -q WITH_OPENSSL;then 
-            wsrep_log_info "NOTE: socat is not openssl enabled, falling back to plain transfer"
-            encrypt=-1
+        if [[ $encrypt -eq 2 || $encrypt -eq 3 ]] && ! socat -V | grep -q "WITH_OPENSSL 1";then
+            wsrep_log_error "Encryption requested, but socat is not OpenSSL enabled (encrypt=$encrypt)"
+            exit 2
         fi
 
         if [[ $encrypt -eq 2 ]];then 
@@ -204,11 +204,11 @@ get_transfer()
             fi
             stagemsg+="-OpenSSL-Encrypted-2"
             if [[ "$WSREP_SST_OPT_ROLE"  == "joiner" ]];then
-                wsrep_log_info "Decrypting with PEM $tpem, CA: $tcert"
-                tcmd="socat -u openssl-listen:${TSST_PORT},reuseaddr,cert=$tpem,cafile=${tcert}${sockopt} stdio"
+                wsrep_log_info "Decrypting with cert=${tpem}, cafile=${tcert}"
+                tcmd="socat -u openssl-listen:${TSST_PORT},reuseaddr,cert=${tpem},cafile=${tcert}${sockopt} stdio"
             else
-                wsrep_log_info "Encrypting with PEM $tpem, CA: $tcert"
-                tcmd="socat -u stdio openssl-connect:${REMOTEIP}:${TSST_PORT},cert=$tpem,cafile=${tcert}${sockopt}"
+                wsrep_log_info "Encrypting with cert=${tpem}, cafile=${tcert}"
+                tcmd="socat -u stdio openssl-connect:${REMOTEIP}:${TSST_PORT},cert=${tpem},cafile=${tcert}${sockopt}"
             fi
         elif [[ $encrypt -eq 3 ]];then
             wsrep_log_info "Using openssl based encryption with socat: with key and crt"
@@ -218,11 +218,21 @@ get_transfer()
             fi
             stagemsg+="-OpenSSL-Encrypted-3"
             if [[ "$WSREP_SST_OPT_ROLE"  == "joiner" ]];then
-                wsrep_log_info "Decrypting with certificate $tpem, key $tkey"
-                tcmd="socat -u openssl-listen:${TSST_PORT},reuseaddr,cert=$tpem,key=${tkey},verify=0${sockopt} stdio"
+                if [[ -z $tcert ]];then
+                    wsrep_log_info "Decrypting with cert=${tpem}, key=${tkey}, verify=0"
+                    tcmd="socat -u openssl-listen:${TSST_PORT},reuseaddr,cert=${tpem},key=${tkey},verify=0${sockopt} stdio"
+                else
+                    wsrep_log_info "Decrypting with cert=${tpem}, key=${tkey}, cafile=${tcert}"
+                    tcmd="socat -u openssl-listen:${TSST_PORT},reuseaddr,cert=${tpem},key=${tkey},cafile=${tcert}${sockopt} stdio"
+                fi
+            else
+                if [[ -z $tcert ]];then
+                    wsrep_log_info "Encrypting with cert=${tpem}, key=${tkey}, verify=0"
+                    tcmd="socat -u stdio openssl-connect:${REMOTEIP}:${TSST_PORT},cert=${tpem},key=${tkey},verify=0${sockopt}"
                 else
-                wsrep_log_info "Encrypting with certificate $tpem, key $tkey"
-                tcmd="socat -u stdio openssl-connect:${REMOTEIP}:${TSST_PORT},cert=$tpem,key=${tkey},verify=0${sockopt}"
+                    wsrep_log_info "Encrypting with cert=${tpem}, key=${tkey}, cafile=${tcert}"
+                    tcmd="socat -u stdio openssl-connect:${REMOTEIP}:${TSST_PORT},cert=${tpem},key=${tkey},cafile=${tcert}${sockopt}"
+                fi
             fi
 
         else